documentcloud/underscore — pull request #351 by kitcambridge (2011-10-26 04:50:57+00:00)
Title: `_.isEqual`: Use `[[Class]]` checking for consistency and performance.

These changes are likely to be controversial, but I thought they would merit some discussion now that #321 has been merged...

* Objects with different `[[Class]]` names are no longer equivalent.
* String, number, and boolean primitives and their corresponding wrappers (e.g., `"5"` and `new String("5")`) are now equivalent.
* Arrays are now recursively compared by their numeric properties only. All non-numeric properties are ignored.